1. Field of the Invention
The present invention is directed to a motor mount for a dishwasher and particularly to a motor mount for mounting a motor to a pump in a dishwasher in order to prevent transmission of vibration and noise from the motor.
2. Description of the Prior Art
The use of motor-driven rotary shafts in combination with fluid pumps is well known. A motor is typically mounted in a fixed location relative to a pump, either to the pump itself or to structure which is also fixed relative to the pump.
A problem associated with such designs is that vibration created by an electric motor, normally occurring at twice the electrical line frequency, is transmitted to the pump, and causes the pump to vibrate at the same frequency. A typical electrical line frequency is 60 Hz, which results in a relatively low transmitted vibration frequency of 120 Hz.
In an application for a pump such as a dishwasher, where the pump is mounted to a tub having relatively large rigid walls subject to resonance, a high amount of low frequency vibration is transmitted from the pump, causing the tub to resonate and creating an unacceptable noise level. Such low frequency vibration is difficult to absorb using conventional noise absorbing or insulating materials.
In U.S. Pat. No. 3,500,754, Boes et al., an electric motor is end-mounted on a horizontal centrifugal pump. The casing of the electric motor is connected to the pump housing by screws which pass through vibration-absorbing and heat insulating bushings.
U.S. Pat. No. 2,880,740, Peglow, shows a means for preventing transmission of vibration in a dishwasher in which vibration damping material is disposed between the motor-pump combination and the dishwasher tub. An elastomeric ring is provided, having an upper annular portion connected to the bottom wall of the tub and a lower annular portion connected to the motor-pump combination. Tension is maintained on the elastomeric ring to suppress transmission of vibration to the dishwasher tub.
U.S. Pat. No. 3,446,155, Guth, shows shock-absorbing means for mounting a motorized pump assembly to the shouldered sump opening of an automatic dishwasher, comprising a flexible, generally planar solid ring-like boot. The boot provides both vibration dampening and water sealing functions.
In U.S. Pat. No. 4,822,241, Jarvis et al., assigned to the assignee of the present patent application, an automatic dishwasher includes an electric motor end-mounted to a pump housing in a horizontal configuration, with the motor being rigidly supported at three support points.
Therefore, it is known to isolate vibration in a motor-pump combination by providing flexible boots and bushings. A disadvantage of such vibration isolation systems, however, is the inability to permit torsional motion of the motor, while preventing undesirable radial motion of the motor. Another disadvantage of known vibration isolation systems is the requirement of soft, resilient members subject to degradation over use and time.
Another disadvantage of known vibration isolation systems is the inability to permit torsional motion of the motor, while preventing undesirable axial travel of the motor. Yet a further disadvantage of known vibration isolation systems is the inability to, in a cost-efficient manner, end-mount a motor in a dishwasher while preventing transmission of unwanted vibration to the dishwasher tub.